Aluminum Brazing Sheet Interliner for Flux-Free CAB Joining
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Solution Overview
Problem
Current Controlled Atmosphere Brazing (CAB) methods rely heavily on flux to prevent oxidation during aluminum part joining, which poses environmental health and safety concerns and leaves residual flux on components, prompting the need for flux-free brazing solutions.
Innovation Solution
A sheet material comprising a core layer of 3XXX, 1XXX, or 6XXX series aluminum alloy with an interliner layer containing Mg, Si, Bi, and optional additional elements, sandwiched between a brazing liner layer of 4XXX aluminum alloy, allowing for flux-free brazing in an inert atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flux is used in CAB brazing to protect metal surfaces from oxidation, then the brazing process reliability is improved, but environmental health and safety concerns increase and residual flux remains on parts
Solution Approach 1:
The patent removes the flux component from the brazing process entirely by using a controlled atmosphere (inert gas) to protect metal surfaces from oxidation. The inert gas environment replaces the chemical protection provided by flux, eliminating harmful flux residues and environmental concerns while maintaining brazing reliability.
Solution Approach 2:
The patent employs an inert gas atmosphere (such as nitrogen or argon) to create a protective environment during brazing. This inert atmosphere prevents oxidation of metal surfaces without requiring flux, thereby eliminating the harmful effects associated with flux while ensuring successful brazing outcomes.
2Manufacturing precision
If flux is used in CAB brazing to remove oxide from parts, then the joining quality is improved, but residual flux contamination occurs on components
Solution Approach 1:
The patent extracts the flux substance from the brazing system and replaces it with an inert gas atmosphere. This eliminates the source of residual flux contamination while maintaining the ability to remove oxides and protect surfaces through the controlled inert environment, ensuring clean components after brazing.
Solution Approach 2:
The inert gas acts as an intermediary medium that performs the protective function previously fulfilled by flux. The inert gas atmosphere mediates between the metal surfaces and oxygen, preventing oxidation without leaving any residual contamination on the components.
3Adaptability or versatility
If a multi-layer clad structure is implemented for flux-free brazing, then the brazing capability without flux is achieved, but the manufacturing complexity increases
Solution Approach 1:
The patent divides the metal sheet into multiple functional layers (base metal layer, intermediate layer, and brazeable outer layer) with specific compositional ranges. Each layer serves a distinct purpose: the base metal provides structural integrity, the intermediate layer controls oxidation and promotes wetting, and the outer layer enables flux-free brazing. This segmentation allows flux-free brazing capability while managing manufacturing complexity through standardized production processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables effective joining of aluminum parts without flux residues, reducing environmental concerns and maintaining the cleanliness of heat exchanger components, while also offering cost savings and improved operational efficiency in the brazing process.
Implementation Method 1
the surfaces to be joined and the filler metal need to be protected from oxidation during the various stages in the brazing process
Implementation Method 2
melting the filler metal, which flows into the interface between adjoining parts by capillary action and hardens upon cooling to join the metal parts
Implementation Method 3
a brazing liner layer of 4XXX aluminum alloy
Data Source
AI summary
An aluminum alloy brazing sheet has a 3XXX, 1XXX or 6XXX core, an interliner and a 4XXX brazing layer without added Mg. The interliner has Bi and Mg, the magnesium migrating to the surface of the brazing sheet during brazing and reducing the aluminum oxide to facilitate brazing without flux in a controlled inert atmosphere with reduced oxygen.